Rockville Mayor Phyllis Marcuccio warned that the “friendly competition” that exists between her city and Gaithersburg could become less friendly if Gaithersburg continues to try to annex a property along Shady Grove Road.

“This puts it on a much more, let’s say, firm platform of competition,” she said. “Which can be good, but is also sad at the same time.”

The land sits just south of Gaithersburg city limits and is within both cities’ maximum limits, according to county planning documents.

Marcuccio’s comments came after a Monday hearing before the county’s Planning, Housing, and Economic Development Committee during which she noted the city’s opposition to Gaithersburg annexation plans, saying the two cities previously have agreed that Shady Grove Road would be the dividing line between them.

She said the two cities have long held a friendly rivalry between schools and business interests — one honored by cooperation.

“It was pretty clear that we would always honor each other whenever there was a connection between the communities,” she said Monday.

Marcuccio said Shady Grove Road is an “unwritten barrier” between the cities, with Gaithersburg to the north and Rockville to the south.

She said if Gaithersburg continues with its effort to annex the Sears property, her city likewise could begin to ignore the boundary.

“What it says is our artificial boundary is not a boundary,” she said.

Gaithersburg Mayor Sidney Katz said he could not comment on the annexation or Marcuccio’s comments until after the city closed its public record on July 5. The city is expected to take action to annex the land in August.

The Sears property could open the door for Gaithersburg to expand further alongside southern Shady Grove Road, property Marcuccio said Rockville has plans to own.

These plans include the possibility of the U.S. Post Office building to the west of Sears, which could be foiled by Gaithersburg expansion as the land to the south of it is a solid waste transfer station — a waste dump — owned by Montgomery County. The county dump and the Sears property would create a kind of barrier prohibiting Rockville from annexing property immediately to the west of them.

The U.S. Postal Service announced May 17 that it had plans to close its Suburban MD Annex facility in Gaithersburg as part of a larger effort to consolidate its locations around the country.

County Councilman Marc Elrich said Monday he hoped the cities would be careful about annexing land, particularly if it brings new construction. He said the idea of municipalities wooing property owners to seek annexation worried him.

“This county has consequences for decisions you make,” he said.

The Sears property alone represents $12,285 in lost revenue to Montgomery County, according to figures by the county Planning Department.

Montgomery County cannot, by law, prohibit Gaithersburg from annexing the property, said county Legislative Attorney Jeff Zyontz on Monday. Cities can annex property along their border at the request of property owners.